Automotive hydraulic braking system



Janm 3, 1950 R. H. zx-:ILMAN AUTOMOTIVE HYDRAULIC BRAKING SYSTEM Filed July 24, 1945 Patented Jani 3, 1950 UNITED# PATENT OF F ICE? AUTOMOTIV HYDRAULIC BRAKIN G SYSTEM Ohio, assigner to' The The'w ShoveliCompany, Lorain, Ohio, a corpo-l A ration i@rollio Application July-124, 1945, Serial-No. 606,793n

lorakesystems have` been emplyedf'for heavy vehicles.-

Inthe Vprioruse .of air. brakes, a` source of lbrake energizing pressureis'. provided. by a source offair maintained u-nderhigh. ypressure supplied by a motor driven pump. of any'sultabletyp'e; it being necessary in such -a system'to .prei/idea 'niotrdriven air compressorandother.apparatus ancillary thereto includingapressedlair tank tothe equipment normally carried.' by the automotive vehicle; in .suchiair brakesystms, Vtheiopjera'tcir directs a flow of .highly compressed 4air to suitable fluid pressure responsive, ,brake .operating .devices by the actuation aofi ain. valvesN which Aobviously may be operated byhandior. foot power..

Hydraulic bra-king. systems? have been found more practical -and..reliableiorh passenger.A automobiles,where vmost commonly, theoperator, by

actuation of-v afbrakeL pedalor handlever, communicates foot or hand power to a confinedibody of hydraulicliuidsuch assoil, andbyfvirtue of conduits leading-drum" such coniined hydraulic fluid to brakei operating: -fl-uid responsivef diaphragms -or-pistons, thefpowerrsm createdis transmitted' to the vehiclebrakes.`

However, since hand or foot power is insuircient for vthe purpose .of :adequately-brakingheavy vehicles `of the aforesaid class; it f isfan': object fof my present invention.tozprovidecelectrical.power means forfsupplementing' theieiirt AofV theivehiele operator;l .whereby fa.- greatly4 increased: r'hydrau'lile cally transmittedk brakin'gielort isicommuni'cated -to the vehiclewheelsgwhich; at fal-.l timesiseund'er the `control of the lusual personally operable braking apparatus.

Although it has previously been proposed? to apply fa compressed air pressurefsystemf-foractuating the: brakes-- of ian@ automotive vehicle-to a hydraulic system voff' lower=` power which'v A is: l persona'lly controlled 'by theI operatroff'thewehicle, the` application oi the compressed`air"equipmerit involves a clearly-increased'expense-inthe vehicle carried equipment, saidequipment also taking'up considerable.spacefonthe-vehilefwhiclrcanmore 2 v advantageously be employedior other utilitarian purposes.

Alll commercial types of automotive vehicles now commonly are'provid'edwith a storageb'attery which'isstandardV equipment 'and I therefore utilize current' from said storaf'gel battery fork energizationofan electric motor which, in turn, is adapted Lto actuate' and/or retract a hydraulic compressor Vof 'thetype' employing a reciproc'able piston whichis adapted 4'toperate under the control of` a' foot power' compressor for hydraulic fluid, and when so operated'is adapted lto greatly increase'the hydraulicpressure of Afluid applied to the hydraiilic pressure responsive braking f motors;

An object of the 'presentinvention is to provide a heavy 'vehicle' with an electro-'hydraulic power brakingapparatus'and"system which may be supplemental't, operable'under the control of; and be operated responsive tothe operationofa personally actuated liquid pressure braking system which is, irrnoway,A nor to any degreedisabled t'o apply a p'ersonailycreated braking 'effort to the vehicle Wheelsshould the auxiliary controlled power braking apparatus become inoperative; or be out of operating conditions.

Another objectv ofmy invention is to' provide an improved hydraulic' braking system for 'heavier vehicles than cana'dequately bebrakedby the personal effort'of theoperator, which isoperable throughv the instrumentality of an 'electricf'motor energizable `from a vehicle carried electrical storage battery and operated under thecontrorlA of the same brake pedal or other lever winch,` i'f-the motor means is inoperative', isfope'rative toapply aA personally ycreated braking effort" to the wheels of the Vehicle:

Other objects o'finyinvention and'fthe invention itself will be obvious totlrose skilled inthe art by reference'to 'the following specification `of a preferred embodiment of'my invention and Ito the accornpanyirig'A drawing illustrating 'the'v said embodiment.

Fig. 1 is a dia'granimaticlview of anl embodiment :of myinvention Fig. 2 shows; dia''gramm`atica'lly,I an alternate arrangement 'whereinastarting switch; ordinarily hydraulically operated, may be `op'eratedby 'the provision'o `a mechanical linkbetween the Abrake pedal and the switch.

The drawing is a' diagrammatic 'view 'of merely one embodiment U@01*th'e invention, the: various parts indicated not being 'to auniform scaley the proper'sizes of the-various operativev parts for any vehicle being susceptible ofl as'certairrr'nent` ac- 3 cording to well known engineering principles, when the number of wheels to be braked and the weight of the vehicle is known.

Referring now to the drawing, at B I show two of any desired number of fluid brake cylinders, according to the number of vehicle wheels to be braked.

Each of said cylinders, as is well known, comprises a movable element, such as a piston 2 and attached piston rod 2', the latter adapted for attachment at 3 to the operative lever (not shown) of a friction brake mechanism for a vehicle wheel, whereby when the piston rod is further extended from the cylinder, said lever applies the friction brake to a. degree dependent upon the outward thrust of such rod.

At P, is shown a vehicle brake pedal of any well known type, normally maintained in retracted position, as shown, by a spring 4, being journalled upon a cross shaft 5.

The pedal P provides by an extension 6, an operating lever, iiexibly interlocked between projections 'I of a piston rod extension 8 of a pi-ston 9, which is telescoped for reciprocation within a cylinder I0 to provide a liquid compressor. The spring 4, through the pedal lever 6, normally maintains the piston 9 in the inoperative position indicated. At I I, I show the periorations of walls of the cylinder I0, which provide inlet ports for the cylinder, said ports II being normally in communication with a. supply of liquid, such as oil, maintained in the box I2, which is relatively more elevated than any other part of the iiuid system, whereby the cylinder and the iluid system is normally maintained full of well known ways. Any well known expedients, not here shown, are employed whereby the presence of air in the fluid system is avoided, and to ensure that the system is maintained lled with liquid.

A conduit I5 having a valve housing 58 interposed therein extends from the discharge port I3 of the cylinder I0 to the cylinders B, via the cylinder IE, conduit I1, and like branched conduits i8.

The pedal P, when personally depressed, is, therefore, initially adapted to move the piston 9 inwardly of the cylinder Ill, rst to close the inlet ports II, then to force the oil thus trapped through the outlet port I3, into the conduit I5, which, as previously stated, leads to the brake cylinders B.

The liquid forced from the pressure cylinder ID, into the conduit I5, thus causes displacement of liquid in the conduit means cylinders and so increases the pressure of liquid exerted against the brake pistons 2 as to cause them to move the piston rods 2 outwardly to a sufficient degree to initiate braking effort upon the brake mechanisms, not shown, which are respectively associated with the vehicle wheels, equipped with such mechanisms.

The personally effected pressure of the vehicle operator upon the brake pedal P therefore is effective to accomplish a substantial degree of braking effort upon the vehicle Wheels, independently of any operation of the piston I4 of the cylinder I6, which cylinder, not shown to scale, is much larger than the cylinder Ill; the length of the piston stroke of the piston I4 is preferably and assumed to be greater than that of the piston 9. The piston I4 is adapted by the apparatus illustrated in the drawing to be operated by an electric motor M through reduction gearing comprising the worm 5I gear 52, and rack pinion 53, said oil in one of many leading to said brake gearing being preferably iiexibly driven by any suitable form of iiexible coupling, generally indicated at B5, which is provided to lessen the starting shock upon said gearing, which may be in Widely variant forms, only one of which is shown in the drawings, the principle being generally indicated at I9; however, in the event of failure for whatsoever cause of the motor M to operate the piston I4, the physical eort of the vehicle operator exerted upon the pedal P is thus apportioned among the brake mechanisms served by the cylinders B, and which in number will preferably be equal to the number of braked wheels with which the vehicle is provided.

By virtue of the above motor-operated power compressor, I have provided in the system of my invention, an auxiliary source of highly increased hydraulic pressure, for increasing the braking effort, comprising said motor and gearing. The motor M may preferably be of the direct current shunt wound type, whereby after the piston has been initially advanced by said motor to apply the brakes, reversal of the energizing current supplied to its eld winding is effective to cause the motor to rotate the motor shaft 50 in the alternate direction of rotation to retract the piston I4.

Through the instrumentality of the intermeshed worm pinion 5I and intermeshed worm gear 52 together with the rack driving pinion 53,

: 'i which with the worm gear 52 is keyed onto the shaft 54, the rack 55, which is intermeshed with said rack pinion 53, may be thrust in either longitudinal direction by rotation in the desired direction of the reversible motor shaft 50.

At 56, I show an electromagnetically operated valve mechanism comprising a lowermost compartment containing a solenoid electromagnet 57 and the upper part comprising a valve housing 58. A Valve stem 59 provided with a pair of valves 60 and 62 is so disposed in the casing 5G as to be downwardly reclprocable to close the valve ports 6I and 63 against the power of a spring 65 which exerts pressure to press the valve stem 59 toward its illustrated uppermost valve opening position.

' To the lower end of the valve stem 59, I preferably provide an electromagnet armature 66, rigidly afxed thereto, and adapted upon energization of the electromagnet 58, to move said valve stem downwardly to simultaneously close said valve ports.

The duplicated valves are so arranged as to be oppositely affected by hydraulic pressures at either side, whereby such hydraulic pressure does not tend to move the valves which are diiferentlally balanced with reference to hydraulic pressure.

The electromagnetic circuit for the armature 66 preferably comprises said armature, the walls S1 of the electromagnet compartment 56, and a core element 530 which extends partially upwardly through the bore of the electromagnet in the axial direction of the armature 65 which is normally longitudinally spaced from the end of the core element 58, and magnetically attracted thereto to simultaneously operate the valves when the magnet is energized.

For the purposes of suitably controlling the energization of the motor M, I provide a pair of hydraulically operable switches S and Sa, which are, respectively, adapted to be operated by the hydraulic pressure device indicated at 20 and by the switch key K which is carried by the piston operating rack 55. The device 20 is preferably proy vided with a switch operating snap-action element which is preferably supplied by the diatype," 'disclosed-insomewhat similar formv inv the` prior'patent to Levy; No; 1,781,287,- dated- N ovem-` ber^'11, 1930".-`

However, any other known vfluid operated switch mechanisml whichiis adaptable to' operate the contact"`sets withfa"Snapactionresponsive*v tothe applicationl and fcessation lof fluid pressure maybeemployed;

The switch mechanismfs'bicomprises tWo'pairs of switchpontacts "1l and"l`2, the associatedcontacts `of which are znormally-A broken-by normal interposition' of "the'keyj l'which' isccarriedA byA the. rack 55 "betweenthe" outermost switchA contact 'springs-1| andJlZ". These pairs of contacts are "adapted'to be closed upon -movement of Jthe rack -55finsufch direction-as to thrust pistonC I4 inwardlyofthe cylinder 16; said' contactsbeing subsequently" adapted"V to` be reopened with a snap action upon'meturn'of said rack toi'vthev normal position:

The' snap action breaking-ofthe `switch contacts is achievedbyvirtue-of the spring which' is compressed when the key K engages the curved endsmof 'the vcontact springs'll andl 72 which resistfurther'movement of the key suiiciently-to effect-telescoping ofthe end=82 ofthe key into th'e slideway' of'ther element 83 carried by the end* of th'e'racku 55;'- until` the pressure vof thethereby' compressed-spring isV suii'icient to snapthe end of thekey-Kibetweensaid curved endsof said control springs.

Whiley the actuating means` for both of lthe switch means-S andi-Scare 'preferably' of thesame-'typey each-'comprising a fluid' pressure de'- il vice comprising reversibly buckled springfdia-` phra'gmsZZ and' 23j' respectively; exposed vto pressure of li'quidinthe conduitsA |5and' 48, respec= tively, and each'biased toward normalposition by the-restoringwsprings 28"-and46l, respectively; the spring46= for thegd-iaphragm 23 is, however; a much heavier spring-:than `theVv spring- 28 which is relatively lightL and the-'diaphragmf23 is of thin'-` nerfI spring 'metaL whereby theactuating diaphragm' l22for-the-switch-rneans Sa is operated only upon communication' of a much greater valueofliquid pressure communicated tothe upper'ssideiofcthieldiaphragm A235" Ineach case; and more importantly for-theswitch Sa, the opposing pressure veliect' of-v said' springs Auponl thed respec` tive diaphragmsis susceptible of predetermined adjustment by suitably threading the oaps-29 and 49-"on 5thf'e-lrespeotive Adiaphragm housings.`

The1pressuredevice 20s-:is therefore susceptible tofoperationvery shortly after the-'piston Sfhas passed# the-ports Il butuntilthe motor` has caused withdrawal of-' the plug-K from between the springs 111 and i12-1, continued 'movementfoiI thebrakepedal P-will add' tothe pressure of l-iqui'd'in' the 4lines@ l5,l` l1 andllS.l particularly- Whenfthe pedal P is -lmoved with'vmore than ordinary power and speed; but usually'the power ac-z tuated 'pistonl dewill'4 behsubstituted 4for therpistcn Sfasftheesource of'hydraulic pressure foropera-tingsthe V2brake'sfbefore--l the piston f 9' has built up a-sub'stantial amount ofpressurefin said lines; The'diaphragms-'H and A23fare each so .formed thatlwheneversuilic'ientluidI pressurey is applied tothe convex surface-of 'the diaphragm, downward lmovement l ofsaid central portion occurs to cause thecentral-portionv of-`the diaphragmv to -b'e rapidlyreversely' buckled-,2' by so--ca-lledv snaps action, whereuponeitsiu-pper' sidev is concave and lower sidet convex, andff-suchsnap-action movement-ein either=directon is-communicatedfto certain of' many v-forms of= snap action idevices which'r can' be advantal'geously-` employed to ensure, that the illustrate'difcontact I pairs which conduct relatively heavydirect current ilows, will bev-brok'-`A en with sufficient rapid movement. of. the movable:

elementsof the switches,` as tti-'prevent the draw,-

ing out of an arcwhichotherwisemight befcon. tnuous and destructive of thef. contacts.

However,A Iam'aware that electrical switches. wherein contacts aref'broken with a snap: action are well known in many forms and with many different` kinds oir snap action ,instrumentalities associated therewith, and I therefore contemplate the use of anysuitable instrumentality for any ofthe switches disclosedintherpresent specification and drawings.y

In order to minimize the arcingf at lswitch.4 con-- tacts, I am* awareofthe well known 'practices-ot suppressing the electrical inductive discharges emanating from th'ewindingsy of-1motors,1 electromagnet windings and' the' like;- consistingdoff thebridgingA of such* windings -A by; condensers, ressn tors, or combinationsthereof; as-wellknown in*- the' electrical arts; and althoughll illustration thereof is here omitted,H I therefore contemplate suitable usev of suchr devices ifor-the electromagnet winding 57 'andthe motor' windings,- but; inv any case, I deem it important that breaking of switch* contacts carrying-"heavy direct Icurrents advisedly should beachieved-withl -the movableelement thereof d moving' atA al high rate=of f speed, and this is suitably accomplished by' provision of lsnap-- action instrumentali'ties;4

Whereas I have llustratedthe` hydraulic actuator 20 `forV actuating the-switch S; it will be understood that actually theepedal'Pis the-primary, actuating means forl said `switch`- and that the vpistonv 9;'the column of'liquid inA` thecylinder I0, and conduit means l5--25,` and the diaphragm carried4 rod-26; are merely 'motion transmission meanstotransmit switch operatingmotion fromV the pedal Ptosa-id switch. The structure for operating the switch Sco-uld, therefore; be simplified by employing a suitable-mechanical movement element; as shown in Fig. 2, such as the spring interconnectingl any suitable element ofthe pedal, such as an armr Z, with the element-261- of the-switch S1, there being incorporatedwin su'chan arrangementak suitable annularholder 201fifor a resilientfdished diaphragm 221, the switch blades thus being assembledtogeth-er' but' insulated fromY each other and the assemblyis connectedl to the central portion of the disc. It will be obvious that movement of the pedal P will exert tensile stress upon the element lwhich is joined to the central portion of the disc', and by a-snap action ofthe discwi'll remove the switch blades-301 3I1, 3'21v'and 331 iny substantially-the same manner as the corresponding switchV blades at Sin-Fig. 1, to directly operate said switch' from saidpedal, by interlinking said pedal P and said rodi261j the diaphragm 23 or any similar-f snap action device: 23n merely. serves, inv any case, -to effectl/snap-action breaking lof the switch contacts. f i The hydraulic devicef-'Z-lllere disclosed permits variation of preferred placement of the switch S, to accommodate my preference that such switch be positioned near the motor M, to simplify my preference to build the motor, power compressor, and controlling means as a more compact unit, and which purpose is well served by use of the disclosed device 20.

The booster brake controlling system is preliminarily conditioned for operation by first operating the manually operable switch Sw whereby current from the storage battery carried by the vehicle is communicated to the conductors 40, and said manual switch is maintained in operated position throughout every period of vehicular travel, requiring use of the power-actuated braking mechanism, herein disclosed.

Other auxiliary locking or wheel braking means, not shown, are employed to hold the vehicle stationary during periods when vehicular travel is not desired.

Compression motor starting operation The switch S being operated, as previously described, closure of the normally open contacts associated with the switch blades 30 to 33 inclusive is effected, thereby closing energizing circuits for the compressor motor, as follows:

Battery current from the source D. C. is concurrently supplied to the motor armature terminals, first, by the conductor 36 which connects the negative conductor 40 to the armature terminal A, and second by the normally open but now closed contacts associated with the blade 33 of switch S, which extend a circuit from the positive terminal of battery to the armature terminal A', through positive conductors 40 and 41', the lowermost normally closed contacts associated with blade 35 of the switch Sa, the conductor 31 leading therefrom to said now closed contacts for the blade 33, and this circuit including the conductor 31 leading from said blade 33 to the said armature terminal A'.

The motor is now operated to rotate its shaft 50, the worm I and reducing gearing 52 and 53, to drive the liquid contained in the cylinder I6, thereby to apply the very high pressure of said liquid through conduit ducts I8 to the brake units B to apply the wheel brakes. associated therewith.

switch Sa, through the pair of conductors leading therefrom to the normally open but now closed contact pairs associated with switch blades 30 and 3l of the switch S, and thence to the motor eld winding, not shown, but whose terminals are indicated at F and F. The positive pole of the battery D. C. is thereby connected to the terminal F, and the negative pole to the terminal F.

Currents thus concurrently flow both in the motor field and armature in such related directions of flow that the motor shaft 55 is rotated in such a direction as to cause the worm 5I to drive the gears 52 and 53 counter-clockwise, whereby the rack 55 together with the piston I4, is thrust forwardly to cause said piston to expel liquid from the cylinder I6.

Initial movement of the rack 55 effects closure of the contact pairs 1I and 12 of the switch Sb and the switch operating parts are so proportioned that said contacts are closed before the rack 55 in the forward direction required to advance the piston I4 to compress the piston I4 has been moved sumciently to so greatly increase the pressure of liquid in the cylinder I6, and resultantly in the conduit I5, as to overpower the previously applied personal effort exerted upon the piston 9 by the pedal P.

An undesirable amount of such back pressure reacting upon the pedal P is avoided by the closing of the valve ports 6I and 63 which are interposed in the conduit line I5, said ports being closed by the electromagnetically movable valves 60 and 62 which, when the electromagnet 55 is energized, are moved downwardly to close said ports, by the eiect of the magnetically induced downward movement of the armature 66, attached to the lower end of the valve stem 59.

This electromagnet 51 is energized by closure of the contacts 1I of the switch Sb, and by precedent closure of the normally open contacts of the switch S which are associated with the switch blade 32 thereof. The energizing circuit comprises both said pairs of normally open contacts relatively serially related and with circuit conductors comprising the conductors 16, 38, 45, and

The valve ports 6I and 63 are closed and maintained closed until subsequent retraction of the rack 55 nearly to normal position, as a result of the continued magnetic pull exercised on the movable armature 66 of the electro-magnet which causes its lower end to approach but preferably not to make engagement with the upper end of the stationary core pole 58.

Prior to full engagement of said armature with said pole, the valves and 62 are firmly seated and further movement of the armature 66 is prevented.

Immediately following closure of the valve ports 6I and 53, the motor M continues to advance the piston 55, the contents of the cylinder being progressively expelled into the brake cylinder conduits I1 and I8, and the motor power and the size of the piston and the length of its stroke being so proportional that the vehicle brakes are applied with much greater pressure than previously personally initiated merely by operation of the pedal P; continued depression of the pedal P to maintain the switch S operated, as described, will soon cause the brake mechanisms to be as fully applied as is desirable, by application of fluid pressure resulting from forward movement of the piston I4, applied to the pistons 2 of brake cylinders B.

The high degree of liquid pressure thus communicated to the conduit I1 is also concurrently communicated by the duct 48, to the preferably upper normally convex side of the diaphragm 23 provided for operating the electric switch Sa, and until a predetermined maximum fluid pressure is achieved, whose value may readily be ascertained from the fluid pressure indicator I, which communicates with the conduit 48 and is preferably located upon the operators instrument panel in the driving compartment of the vehicle.

The adjustable cap 49 having been suitably preadjusted to so compress the spring 46, that such predetermined maximum pressure will be sufficient to overcome the resistance offered by said spring pressed diaphragm whereby the liquid pressure at said maximum value will effect reversal of the direction of buckling of said diaphragm whereby said diaphragm will operate the switch Sa., to snap the blades of its contact sets 34 and 35 to open circuit position.

Opening of the contact pairs 34 `and 35, while 75 the switch S is operated to maintain the contact pairs .-3.0.and73l closed, interrupts the energizing armatureand. '.'eld circuits.. of the. motor M and discontinuos .thehydraulic compression for- Ward movement .ofthe rack 5'5fand, withmotion. of; the piston li4..arrested..a't some. such indicated position .as rc,..said =maximum-pressureis continuously applied. to;..the brake units "B, .until such time .as the operator, .by releasingA the pressureiuponthepedalPrrestores the switch S to normalposition.

Thus, .excessive braking 4pressure votherwise achieved by forward braking movement of the pistonidis avoided, since operationofthe switch.

Sa causesits switch `bladesto break .the energizing armature and .field .motor circuitspreviouslyfdescribed, said.circuits bothfbeinginterruptedbysaid .breaking of thefcontacts 34 and '35,.which are serially. included in'both said motor energizing. circuits, at `this '.time.

Restoring Operation The "operator, iat :any-.time during' ener-gization of :the motor M, 'mayinterrupttheforwardzmovement 'ofthe '.piston 124 .iby;merelyireleasing the.y foot pressure ipreviously :exerted .upon .the pedal kP. Such release v-of :the "pedal P, whether leffected during operationof" the motor.M,. to. advance the piston or after'fthemotor. stops ;.due to aforesaid operation: of-ftheiswitch` Suasa result; of maximum liquid pressure bein-g achieved,.isieiectivettdeiect its .terminalA.remainingconnected through rconductor36, to t e vnegative terminal. of thefbattery D. C., and yits a terminalV A 1 through :conductor '-3 1', the reclosed:normalicontacts of `blade set `133 of the .switch aS, .conductors i6 and `I6, andtthel 01T- normal, "now vclosed contact;pair' l2'foff the .-'switch Sb.

The motorffi'eld winding iszconcurrently energized, 1 but" by :reversed owi'of currentfby reclosing of the normal contactsincluding the switch blades 38. and 3l., wherebycurrent; from .the battery :is reversely .supplied through `olf-.normal closed ycontacts .'Hv and l2 vof .the-switch Sib, to 'saidblades 3lirand-3i and-,the conductorsfle-ading from said blades toithe fmotoreld winding terminalsF an'dfF, communicatesuchareversed-current to said'eld IWinding.

The motor, .thu-s reversely' operated continues .to retractf the piston until the, compressionspring 8.5.- suddenly .thrusts `the .plug endof the -key K between .the blades ofthe switchSb whereby said motor iield and motor armature circuits l*are broken .by .the-.now opened contacts 'H `vand 1:2.

Goncurrently breakingof the-contacts oli-the bladesetE which have maintainedcurrent flow through the vvalve operatingelectromagnet 57, n

.de-.energizes said magnet, and the Yrestoring spring "55 restores the magnet armature and the valves Sliand 62to norm-a1.valve-openposition.

Duringretraction .of .the rack r55,1.conseque1f1t toirestorationo'f the switchtherestoring movediameter,

ment of thepiston Ildlof'gtheompression cylinder 1.6 reduces the hydraulicfpressure,exertedthrough theconduit '48 tothe upperside .of the diaphragm 23 whereupon the switchSaJs restoredt'o normal when said hydraulic Apressure reaches a somewhat'lower valve thanjthe above described predetermined'maximum value which is required to initially operatethe diaphragm.

Restoration oftheswlitch Sa, therefore occurs at a time considerably in advance of the time whentherack 55is completely restored tonormal position.

Thefrst' said cylinder vis of relatively small readiness 'for operation, vas* before.

I'have previously stated that'the various instrumentalities illustrate'd'and :described are not illustratedin any uniform scale inthe drawing, the size ofjthe various parts being .largely dictated 'by the relative diiiculties ofjillustrating some of'the 'parts'in the vsznall'size'in other parts are illustrated with respe'ctitc the diametrical sizes vof the cylinder Hrand; piston 9 as compared with the'cylinder I6 andpiston I 4.

'The first. `said cylinder is of relatively small thatthe' pressure offthe operators `foot on the'pedal PmayonlyjbeA asjgreat as a motor vehicle driver commonly-is'a'ccustomed to exert upon the brake pedals of' automobiles and may be of the order of .50 `0r6() lbs., andthe piston 9 andthe innerwalls ofthecylinder l0 may therefore be ofthe orderofl indiameter.

On .the other hand,l thel piston |`4 being, motoroperated through reductiongearing, they cylinder le may be 6to 8 or more in ,diameter depending upon the power ofthemotorMandthe number of'sizes of brake .cylindersB to which saidpressure cylinder I6 supplieshydraulidpressure.

The Speed and'length of the rack'is preferably such as to .achieve the predetermined .maximum high braking hydraulic pressurein a matter of a second or so.

'.The, switchjK. andi-the parts .therefor including the key spring., 85, .and .element..83-. are .shown in relative large scala, but, .infpractica .would be very .small andshort.. as `compared .to the motor operated rack 55 .and voperatinglmeanstherefor.

All. of the above values.- are .susceptible to considerable variation. depending .upon .the Weight and possible-.speedof .the vehicle,.and.=the nature of the brakingifdevices comprising ...the cylinder-s B or their'hydraulic equivalents.

Having .described myinvention y.comprising an improvedsystem. andmethodifor operatingvehicular, brakes forimotorvehicles, Lam aware that numerous land extensive. departures-may bexmade from the system, method .and .apparatus villus-- tratedand/or described, ,Without :however departing .from v.the .principle `and -spirit of my invention.

I claim:

l. Thek combinationfwith an-lautomotivehydraulic i brakingfsystemcomprising y a .l personallyoperablecontrolling brake f-pedal, -a liquid container, a .control compressor comprising a cylinder and piston, a sourceiof .liquid arid-:means for normallyk .disposing said .source Iin communication. with the interior` of vthe cylinder, said means..comprising afportfinaa .wall thereof, said pedal operative yto actuate- -saidpiston .to close said port vandwupon `retraction vof lthe Apedal to restore 4.said piston and open .the port, .a plurality of hydraulic -pressure-eresponsiveexpansible hydraulic brakingxmotors, ,-apcwer compressor com- 7 ,pricingr areciprooablerpistongandfacylinderY therefor, intercommunicatingfconduit, means comprising conduits interconnecting the cylinders of both said compressors and all said motors, pressure transmission liquid lling the space within said cylinders, motors, and conduits, a storage battery, an electric motor, and reduction of gearing adapted to communicate power from said motor to move said power compressor piston, said motor having a pair of respectively eld and armature windings, a plurality of electrical switches, a plurality of circuit conductors extending between said battery, contacts of said switches and said motor windings, means for transmitting motion of said pedal, when actuated and retracted, to respectively operate and restore a first of said switches, a liquid pressure responsive device in fluid communication with said power compressor cylinder adapted to operate a second of said switches under conditions of pre-determined high pressure exerted on the transmission liquid in response to a compressive movement of the piston, a third switch adapted to be respectively actuated and restored responsive to respectively o-normal and normal restored positioning of said power compressor piston, said first switch, when actuated, adapted to complete an electrical circuit from said battery, through certain of said.

conductors, to said motor windings so as to cause said motor to drive said power compressor piston through said gearing in the liquid compressive direction, said second switch adapted to be operated by said device when said piston has moved suiciently to exert said pre-determined degree of high pressure upon said liquid, and said second switch when operated adapted to interrupt the previously completed said circuit for operating the motor, and said rst switch when restored by the eiect of retracting movement of said pedal adapted to complete a modified circuit from said battery through normal contacts of said first switch and oiT-normal contacts of said third switch to said windings in such manner that current will flow through said windings with the direction of flow through one of them being relatively reversed, whereby the motor will be reversely driven to retract said power piston to its normal inoperative position, and said means for transmitting motion from said pedal to said first switch comprising a uid pressure motor for actuating the switch and a liquid lled conduit interconnecting said motor and said control compressor cylinder.

2. The combination with an automotive hydraulic braking system comprising a personally operable controlling brake pedal, a liquid container, a valve device comprising a cylinder and piston, a source of liquid and means for normally disposing said source in communication with the interior of the cylinder, said means comprising a port in a wall thereof, said pedal operative to actuate said piston to close said port and upon retraction of the pedal to restore said piston and open the port, a plurality of hydraulic pressure responsive expansible hydraulic braking motors, a power compressor comprising a reciprocable piston and a cylinder therefor, intercommunicating conduit means comprising conduits interconnecting both said cylinders and all said motors, pressure transmission liquid filling the space within said cylinders, motors, and conduits, a storage battery, an electric motor, and reduction gearing adapted to communicate power from said motor to move said power compressor piston, said motor having a pair of respectively field and armature windings, a plurality of electrical switches, a pluralitv of circuit conductors extending between said battery, contacts of said switches and said motor windings, means for transmitting motion of said pedal, when actuated and retracted, to respectively operate and restore a iirst of said switches, a liquid pressure responsive device in fluid communication with said power compressor cylinder adapted to operate a second of said switches under conditions of predetermined high pressure exerted on the transmission liquid in response to a compressive movement of the piston, a third switch adapted to be respectively actuated and restored responsive to respectively oinormal and normal restored positioning of said power compressor piston, said first switch, when actuated, adapted to complete an electrical circuit from said battery, through certain of said conductors, to said motor windings so as to cause said motor to drive said power compressor piston through said gearing in the liquid compressive direction, said second switch adapted to be operated by said device when said piston has moved sufciently to exert said predetermined degree of high pressure upon said liquid, and said second switch when operated adapted to interrupt the previously completed said circuit for operating the motor, and said first switch when restored by the eiect of retracting movement of said pedal adapted to complete a modified circuit from said battery through normal contacts of said first switch and off-normal contacts of said third switch to said windings in such manner that current will flow through said windings with the direction of flow through one of them being relatively reversed, whereby the motor will be reversely driven to retract said power piston to its normal inoperative position.

3. The hydraulic braking system substantially as set forth in claim 1, characterized by the provision of a valve disposed in a conduit of said conduit means which interconnects the cylinder of the control compressor and the hydraulic actuating motor for said first switch with the said power compressor cylinder and the hydraulic braking motors, said valve being operative to close said conduit, and of an actuator for said valve and means for effecting operation of said actuator, said latter means primarily comprising said pedal and an element of the motor operated actuating means for said power compressor piston, whereby said valve actuator is adapted to be operated responsive to a braking movement of said pedal when said power compressor piston has moved from its normal inoperative position toward its liquid compressing position.

4. The hydraulic braking system substantially as set forth in claim 1, characterized by the provision of a valve disposed in a conduit of said conduit means which interconnects the cylinder of the control compressor and the hydraulic actuating motor for said first switch with the said power compressor cylinder and the hydraulic braking motors, said valve being operative to close said conduit, and of an electro-magnet for actuating said valve and means for effecting operan tion of said electro-magnet, said latter means comprising normally open contacts of said first switch and normally open contacts of said third switch, whereby said electro-magnet is adapted to be energized to close said valve responsive to closure of normally open contacts of said first switch and closure of normally open said third switch.

5. The combination with an automotive hydraulic braking system comprising a controlling piston operated liquid compressor, a pedal for operating said compressor, a plurality of hydraulic pressure responsive expansible hydraulic braking motors, intercommunicating conduit means comprising conduits interconnecting said compressor and said motors, pressure transmission liquid filling the space within said compressors, said conduits, and the expansible elements of said motors, of a power compressor having a hydraulic liquid filled compressor chamber in communication with said conduit means and said motors and a reciprocable compressing element aiording one movable wall of said chamber, a valve interposed in said conduit means between said control compressor and the said motors and power compressor, a storage battery, an electric motor and transmission means adapted to communicate power from said motor to reciprocate said element, said motor having a pair of energizing windings, electrical current conducting means interposed between said battery and said electric motor windings comprising electrical circuit conductors and a plurality of electric switches, one of said switches adapted for actuation and retraction responsive to actuating and retracting movements of said pedal, a hydraulic liquid pressure responsive device and a second of said switches adapted for operation by said device upon communication of liquid at a predetermined high pressure to said device, said device having an actuating liquid containing chamber in communication with the body of liquid communicated to said motors, means operable responsive to oiT normal and restoring movements of said element adapted to respectively operate and restore a third said switch, said rst switch when actuated adapted to communicate battery current to said motor windings to cause said motor to be operated to communicate compressing movement to said element, said rst switch when resto-red and said third switch while actuated cooperatively adapted to communicate battery current to said windings with the direction of current reversed through one of said windings and said third switch adapted when restored to normal position to interrupt the flow of current to said motor windings.

6. A hydraulic booster system for a pedal operated vehicular hydraulic braking system comprising in combination with the actuating pedal, braking hydraulic motors, a control compressor and an operating control pedal therefor, a power compressor comprising a liquid compressing reciprocable movable element, a reversible direct current motor for thrusting and retracting said element from and to a normal position, a storage battery, an electric motor, a hydraulic device operable responsive to hydraulic pressure applied thereto when of a predetermined maximum value, said device in uid communication with said power compressor, conduits interconnecting the exhaust ends of said compressors, and interconnecting said motors and said compressors, means for directing current from said battery to said electric motor rst through the eld and armature windings to drive the motor in a rst direction and thereafter to reversely drive said motor which directing means comprises a iirst electric switch actuable and restorable responsive to actuating and restoring movements of said pedal, a second electric switch actuatable and restorable responsive to off-normal and restored positioning of said compressor element, and a third electric switch actuatable and restorable responsive to actuation and restoration of said device, and electrical circuit conductors interconnecting said battery to said electric motor through varying contacts of said switches, mechanical transmission means for communicating relatively reversed motions from said motor to effect a power thrust effort upon said element responsive to actuation of said rst switch, the first movement of said motor being then terminated responsive to actuation of said third switch, and current from said battery being directed to said electric motor, with relatively reversed direction of current flow through one of its windings, responsive to restoration of said first switch and precedent actuation of said second switch to retract said element and restore said second switch, current now from said battery to both said electric motor windings being interrupted by restoration of said second switch and precedent restoration of Said lrst switch.

'7. The combination substantially as set forth in claim 6, characterized by the provision of a normally open valve in the conduit leading from said control compressor to said power compressor and said hydraulic motors, and electro-responsive means adapted to be energized by current from said battery responsive to operation of said rst switch and of said second switch to effect closing of said valve, and said electro-responsive being subsequently de-energized responsive to restoration of said rst switch.

8. The combination substantially as set forth in claim 6, characterized by the provision of a normally open valve in the conduit leading from the exhaust side of said control compressor, means responsive to off-normal movement of said element to close said valve and said valve adapted to be re-opened responsive to retractive movement of said element.

ROY H. ZEILMAN.

REFERENCES CITED The following references are of record in the fle of this patent:

UNITED STATES PATENTS Number Name Date 2,067,491 Kingsbury Jan. 12, 1937 2,260,490 Stelzer Oct. 28, 1941 2,298,051 Gordon Oct. 6, 1942 2,349,310 Schnell 1-1; May 23, 1944 2,361,419 Schnell Oct. 31, 1944 2,403,870 Martin July 9, 1946 FOREIGN PATENTS Number Country Date 412,965 Great Britain July 6, 1934 

